COMBUSTION CHAMBERS - National Institute of Technology

More documents

Recommendations

Info

INTERNAL COMBUSTION ENGINES (ELECTIVE) (ME667)SIXTH SEMESTERM COMBUSTION CHAMBER ( VTU July 2006)After twenty years of research in 1954, , Dr. Meuner of M.A.N., Germany developed M-process engine which ran without typical dieselcombustion noise and hence it was named ‘whisperengine’.The ‘M-combustion chamber’ is a special type of opencombustion chamber, having combustion chamber in thepiston cavity. It differs in principle from other openchamber designs in that the fuel spray impinges on andspreads over the surface of a spherical cavity in thepiston. Earlier it had usually been assumed that fuelspray impingement was undesirable, though in mostdiesel engines some impingement always takes place atfull load. The fuel is injected tangentially from a multi-hole nozzle on the surface of thechamber in the direction of the air swirl. Injected fuel forms a film, about 0.15 mm thick,on the surface of the chamber. The combustion is initiated by the auto-ignition of asmall portion of fuel which is air-borne at the very beginning. The amount of thisairborne fuel is controlled by selecting a proper distance between the nozzle tip and thecombustion chamber wall. Subsequently the fuel vapours rise from the hot wall and aremixed with the swirling air in successive layers and combustion takes place in a nearhomogeneous air-fuel mixture at the desired rate. The rate of energy release is thusalmost equal to the rate of evaporation of fuel. Thus, even though the engine works ondiesel cycle, once the ignition takes place, the combustion characteristics are similar tothose of OTTO cycle combustion.The advantages of ‘M-chamber Low rates of pressure rise, low peak pressure. Low smoke level. Ability to operate on a wide range of liquid fuels (multi-fuel capability). No combustion noise is reported even for 80-octane petrol.Jagadeesha T, Assistant Professor, Department of Mechanical Engineering, Adichunchanagiri Institute of Technology, Chikmagalur
INTERNAL COMBUSTION ENGINES (ELECTIVE) (ME667)SIXTH SEMESTERThe disadvantages of M-chamber are: Since fuel vaporization depends upon the surface temperature of the combustionchamber, cold starting requires certain aids. Some white smoke, diesel odour, and high hydrocarbon emission may occur atstarting and idling conditions. Volumetric efficiency is low.The following table gives comparison between Open chamber and divided chamber.Sl No.AspectsOpen Combustion Chamber( DIRECT INJECTION)Divided combustion chamber(INDIRECT INJECTION)1 Fuel UsedCan consume fuels of goodignition quality. i.e., of shorterignition delay or higher r CetaneNumberCan consume fuels of poorignition quality i.e. of longerignition delay or lower CetaneNumber2 Type of injectionnozzles usedRequires multiple hole injectionnozzles for proper mixing offuel and air and also higherIt is able to use single holeinjection nozzles and moderateinjection pressures It can alsoinjection pressurestolerate greater degree ofnozzle fouling3 Sensitivity to fuelSensitiveInsensitive4 Mixing of fuelMixing of fuel and air is not soAbility to use higher fuel ratioand airefficient and thus thigh fuel airratios are not feasible withoutsmokewithout smoke due to propermixing and consequent high airutilization factor5 CylinderSimple More expensive cylinderconstructionconstruction6 StartingEasy cold startingDifficult to cold start because ofgreater heat loss through throat7 ThermalOpen combustion chambersefficiencyare thermally more efficientThermal efficiency is lower dueto throttling in throat areasleading to pressure losses andheat losses.Jagadeesha T, Assistant Professor, Department of Mechanical Engineering, Adichunchanagiri Institute of Technology, Chikmagalur
Page 1 and 2: INTERNAL COMBUSTION ENGINES (ELECTI
Page 19: INTERNAL COMBUSTION ENGINES (ELECTI

COMBUSTION CHAMBERS - National Institute of Technology

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?